Many vehicles include a powertrain that is comprised of an engine, multi-speed transmission, and a differential or final drive. The multi-speed transmission includes a number of gear ratios, which increase the overall operating range of the vehicle by permitting the engine to operate through its torque range a number of times. The number of gear ratios that are available in the transmission determines the number of times the engine torque range is repeated. The transmission “upshifts” when it changes to a higher gear ratio, and the transmission “downshifts” when it changes to a lower gear ratio.
Some vehicles are now configured to use active fuel management, in which a portion of a total number of cylinders of the engine may be deactivated under certain circumstances, while the remaining cylinders of the engine continue operation for generating torque. Operation of the engine with active fuel management increases fuel efficiency of the vehicle, but reduces possible torque that the engine may produce because only a portion of the cylinders are being used to generate torque. If the engine is operating with active fuel management when an upshift in the transmission is requested, the engine may not be capable of producing enough torque to maintain the required axle torque, once the gear ratio of the transmission is changed to the higher gear ratio. Upshifting the transmission, when the engine is not capable of producing the required engine torque to maintain the current axle torque in the new, higher gear ratio, such as may occur while the engine is operating with active fuel management, may cause a torque fluctuation, e.g., a sag/surge feeling, that may be felt by the vehicle's occupants.